1. Field of the Invention
The present invention relates to an arrangement for contacting an integrated circuit in a package, in particular for testing the circuit.
2. Description of the Background Art
In order to test the functionality of integrated circuits prior to shipment, these integrated circuits (ICs=integrated circuits), also known as chips, which are generally embedded in packages, are placed in test or measurement boards. By coupling in and out and analyzing test and measurement signals the functionality of the tested integrated circuit can then be determined. The tested integrated circuit is then separated from the measurement board and, depending on the test results, is delivered for actual use or is rejected. Fast and reliable contacting with the measurement board is necessary in order to be able to test the relevant integrated circuits quickly and efficiently.
FIG. 3a shows a conventional contacting of an IC for test. In this context, the chip IC that is to be tested has multiple contact pins CP1-CP4, which must be electrically connected to a measurement board MP. The measurement board MP has test and analysis circuits which are not shown here. Typically-called pogo pins PP or C-contacts CK, for example, are known as resilient connectors between the measurement board MP and the connecting pins CP1-CP4 of the chip IC. In each case, the pogo pins PP and C contacts CK are permanently attached to the measurement board MP.
FIG. 3b shows a detail view of a pogo pin PP constructed of a guide sleeve FH, which has a base F and a mounting pin S, for example for soldering to the measurement board MP. A contact pin CS, which is spring-loaded by means of the coil spring SF, is introduced into the guide sleeve FH. While thin contact pins CS make it possible to reliably contact small connecting pins CP1, CP2, the many mechanical parts make pogo pins failure-prone. Moreover, as a result of the size of the guide sleeve FH, the distance d between the chip IC under test and the measurement board MP is relatively great. In addition, as a result of the small contact area, little or no heat transfer from the chip to the measurement board MP is possible.
The principle of operation of the C contacts CK, which are also known, is shown in FIG. 3c. C contacts are made of metal strips MB bent into a U-shape, one leg of which is attached to the measurement board MP by a mounting pin S. The second leg is then connected at a contact point KP to the relevant connecting pin CP3, CP4 of the integrated circuit IC. The spring action in a C contact CK is achieved by the bending of the metal strip MB. It is also a disadvantage of C contacts CK that the minimum distance d between the measurement board MP and the chip IC is predetermined by the length of the metal strip.
The prior art solutions for contacting chips under test have a number of disadvantages. Heat conduction from the chip is practically impossible due to the small contact area and the great distance of the chip from the measurement board. Moreover, the long conduction paths through the metal strip or the pogo pin result in parasitic effects in high-frequency operation. At especially high frequencies the C-contacts or pogo pins act as antennas, so that reliable testing of such HF circuits in the chip is practically impossible. However, it is not possible in the present day to do without the resilient action of the contact, since modern packages themselves no longer have resilient contact legs. This is especially true of packaged circuits for high-frequency applications. Rather, so-called QFN packages (QFN=quad flat no lead) have no resilient contact legs. Such packages have only flat contact locations on the bottom of the package.